Volume was expected to be light in another holiday-shortened week. The S&P 500 is up nearly 25 percent for the year, and investors are carefully placing bets to make sure they don't erode profits.

Managers are looking at the glass as half full because they want to eke out as much gains as they can through the year. So they're going to view any news positively, said Jim Awad, managing director at Zephyr Management based in New York.

Sales at U.S. retailers rose 3.6 percent for the period from November 1 to Christmas Eve, data from MasterCard Advisors unit SpendingPulse showed. J.C. Penney Co Inc gained 1.6 percent to $27.44, while Amazon.com Inc rose 1.4 percent to $140.43 after it said customers bought more e-books than physical books for the first time ever on Christmas Day.

Airline stocks fell as the United States tightened airline security after a Nigerian man smuggled explosives aboard a transatlantic flight and attempted to blow up the plane. AMR Corp , the parent of American Airlines, lost 2.5 percent to $7.94, while Delta Air Lines Inc dropped 3.7 percent to $11.34.